1. Field of the Invention
The present invention relates to a storage apparatus system (hereinafter also referred to as a “storage system”) for storing data of a computer (hereinafter also referred to as a “server”). In particular, the present invention relates to a storage apparatus composed of a plurality of hard disk units and a technique of controlling a power supply of the plurality of hard disk units.
2. Description of the Related Art
In recent years, various kinds of companies have found it necessary to save all business documents or electronic mail in a storage system under various laws and regulations, and in addition, to enable prompt accesses to the stored data as needed.
A tape device that has been hitherto used as data storing means for storing a large volume of data no longer satisfies a desire to allow prompt accesses to the stored data. Meanwhile, the tape device encounters a problem in that high fault rates occur and there is a significant risk that data is lost or stolen during the conveyance of a tape medium.
On the other hand, a hard disk having a SATA (serial advanced technology attachment) interface has been put into widespread use as a hard disk for a laptop personal computer, which is noted as an inexpensive hard disk compared to a hard disk using a fibre channel interface. Such a hard disk is loaded in place of the hard disk using the fibre channel interface as a recording medium of the storage system, so a low-cost large-capacity storage system can be provided.
With this as a backdrop, a large-capacity storage system equipped with several hundreds to one thousand SATA hard disk units has come into widespread use as the large-capacity data storage means in place of the tape device.
However, the large-capacity storage system that has come into widespread use instead of the tape device is inferior to the tape device in power consumption. The power saving of the apparatus leads to reduction in operating cost of the entire system, resulting in reduction of TCO (total cost of ownership) of the entire system. Some recent reports reveal that the storage system consumes about 20 to 30% of the power in a data center, so how to save the power used for the apparatus becomes one of the biggest challenges for the future.
As a method for solving the above problems, Japanese Unexamined Patent Application Publication No. Hei 09-282057 discloses a technique of controlling on/off states of a power supply of an apparatus. This technique controls the on/off states of the power supply of a peripheral device connected to a computer on the basis of the plan to execute a job on the computer and the way to execute the job.
Further, as another method for solving the above problems, US Patent No. 20040054939 and Japanese Unexamined Patent Application Publication No. 2000-293314 disclose a technique of controlling on/off states of a power supply of a hard disk loaded in a storage system. The technique of US Patent No. 20040054939 controls the power supply on the basis of hard disk in a hard disk group constituting a RAID. Further, in a product manufactured with this technique, the number of hard disks running at a time is reduced to ¼ or less of the loaded hard disks (see http://www.copansys.com/pdfs/Revolution2000TDataSheet.pdf). The technique of Japanese Patent Application Laid-open No. 2000-293314 turns off or saves the power of a power supply of a hard disk of a hard disk group constituting a RAID, which is not accessed.
As the power saving method for the storage system, the related art of Japanese Unexamined Patent Application Publication No. Hei 09-282057 only controls the on/off states of the power supply of the entire apparatus, and there is no description about details of the power supply control such as the on/off control of the power supply of the individual hard disks loaded in the apparatus. This leads to a problem in that it is difficult to respond to an access request from a computer without delay and a power-saving effect is not so large. There is no description about how to prevent the loss of reliability of the individual hard disks due to the repeated on/off operations of the power supply.
The related art of US Patent No. 20040054939 (see http://www.copansys.com/pdfs/Revolution2000TDataSheet.pdf) has a problem in that even when the requisite number of operating hard disks is less than ¼ of the loaded hard disks, it is impossible to expect a power-saving effect as high as an effect attained when the number of operating hard disks is far less than ¼ of the loaded hard disks. In addition, several hard disks that always operate are provided for responding to the access request without delay, resulting in the increase in power consumption.
The related art of Japanese Unexamined Patent Application Publication No. 2000-293314 is such a passive power supply controlling method that the power supply of the hard disk is turned off when there is no access. Hence, it is difficult to respond to the access request without delay. There is no description about how to prevent the loss of reliability of the individual hard disks due to the repeated on/off operations of the power supply.